Bermudians are often heard rejoicing at heavy rainfall and the “good tank rain” it delivers.

But a top overseas scientist has warned the Island’s residents that each time the clouds open, dangerous bacteria is being washed into their tanks straight from the roof.

Professor Eric Dewailly, a public health specialist from Université Laval in Quebec, said untreated tank water could not be considered safe to drink because of the fecal matter from animals it contains.

And he said it was up to citizens — not Government — to ensure they had a clean water supply, especially when infants or seniors were likely to be drinking it.

He told The Royal Gazette: “People realise that there is dirty mud in their tank but they don’t realise that the contamination is coming with each rain.

“Bermuda is fortunate to have access to this rainwater in its tanks and it has to be protected and [the tanks] cleaned.”

He acknowledged, having lived on the Island himself for a year, that tank cleaning was “not an easy job”.

But he explained that a 2004 study he led on the microbiological quality of drinking water from household tanks in Bermuda found that the only procedures “significantly related” to lower contamination were regular emptying and cleaning of tanks and a recent topping up with bought water.

“It’s private water,” he said “It’s not the responsibility of the Government. When it’s your own tank, it’s your own water.

“I know that the Department of Health, they say boil and chlorinate, but at the same time they know or they probably have an idea that nobody is doing it so it’s a way of [the Department[ protecting itself.”

He suggested residents consider having a UV treatment system installed to kill bacteria before the water comes out of the tap.

A call to Clearwater Systems by this newspaper yesterday determined that an under-the-sink system starts at $435 and a whole-house system costs more than $1,100.

Dr Dewailly said: “I know it costs some money but it could be the price to pay if you don’t want to buy bottled water.”

The professor led a fresh study on the Island last year, in conjunction with BIOS and Government, looking specifically for the source of a particular strain of salmonella — salmonella Mississippi — which causes gastroenteritis or diarrhoea and is prevalent here but nowhere else in the region.

The results are still awaited but Dr Dewailly said one likely scenario was that feral chickens were spreading the bacteria, which was then being picked up by birds and deposited on roofs in fecal matter.

“I think the answer will be: it’s everywhere,” he said. “If that’s the answer, then you have to go back to your tanks and fix it. You can’t shoot all the birds on the Island.

“It will be about treating your own water and how to do it properly. It’s down to contamination of your supply and you have to protect yourself from that and there are x number of techniques that can do it for you.

“There are plenty of options for the average Bermudian to treat their water safely. I’m sure the techniques existing today can allow Bermudians to clean their water.”

He said it was especially important to treat the water when youngsters and elderly people were consuming it, as both groups were most vulnerable to disease-causing pathogens.

“It’s probably true that if you suffer from a few [bouts of] gastroenteritis in the year, it’s not a big deal. But it is a big deal for those with immune-compromised systems.

“In these cases, I really recommend boiling the water or buying water. Birds or rats or whatever can carry so many pathogens. Everything is possible.”

A burden of illness study done in Bermuda in 2011 and 2012 found that the prevalence of acute gastroenteritis was highest in the under-five age group.

Dr Dewailly suggested that could be because infants, who have weaker immune systems, were being given unsterilised water.

He said the number of babies hospitalised was “quite high” so it was important to find the source of the problem.

His team of scientists has collected droppings and taken samples from 20 lizards, 20 kiskadees, 50 pigeons, 63 feral chickens and some cockroaches.

“We are waiting to have the final result,” he added. “What we are waiting for is confirmation that it’s all the same agent.

“I’m just trying to find an avenue or solution that could definitively fix the problem.”